Americans overwhelmingly support a more narrow application of the 14th Amendment's Citizenship Clause than the one currently being employed. It's not clear that Congress intended such a broad application of the Citizenship Clause or that a constitutional amendment is necessary to change how births to temporary aliens are handled. For an analysis of the issue, see my report, "Birthright Citizenship in the United States: A Global Comparison."

There are two ways a president could attempt to narrow the scope of the Citizenship Clause: get Congress to write legislation or take executive action.

Legislative option. Though some have argued that a constitutional amendment is necessary to change the scope of the Citizenship Clause — "All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the state wherein they reside" — this would only be true if the clause clearly spoke to children of illegal immigrants and other temporary aliens (e.g., guest workers, tourists, foreign students), and there is plenty of disagreement as to whether it does.

So could Congress direct the executive branch to stop interpreting the Citizenship Clause as broadly as it does now? Seventh Circuit Judge Richard Posner believes so, noting in a 2003 case that "A constitutional amendment may be required to change the rule whereby birth in this country automatically confers U.S. citizenship, but I doubt it." Posner concluded: "Congress would not be flouting the Constitution if it amended the Immigration and Nationality Act to put an end to the nonsense."

Congress routinely authors legislation aimed at clarifying the scope of the Second Amendment — why couldn't it do the same for the 14th Amendment?

Executive action. President Obama has demonstrated that unilateral action by the executive branch is a legitimate means of changing the nation's immigration policy. Many editorial boards have embraced Obama's actions granting work permits and Social Security accounts to illegal aliens. Though his actions have been controversial, executive actions that direct agencies how to approach birthright citizenship are arguably more justifiable.

It is not clear when the executive branch started granting Social Security numbers and passports to children of illegal aliens, tourists and other temporary aliens. But it's standard operating procedure for new parents to simply check a box on hospital forms to request a Social Security number for their newborn and for the Social Security Administration (SSA) to send one out without any inquiry as to whether they are constitutionally required to do so.

A constitutional inquiry is necessary, however, because when it comes to children of foreign diplomats, all sides of the debate agree that these children are not U.S. citizens at birth. Officials at the SSA told me that they know these kids are receiving Social Security numbers, but that they haven't come up with a process to prevent the issuance. Similarly, officials at the State Department told me that they are dependent on diplomats alerting them about births.

All sides of the debate agree that not all children born in the United States should be considered U.S. citizens at birth — the debate is over where the line is drawn. Until there is a reworking of how agencies handle the matter, it appears that the limiting principle found in the Citizenship Clause may have very little effect. (One way in which this lack of clarity presents itself is when a hypothetical child of a foreign diplomat applies for a government job reserved for U.S. citizens with his U.S. birth certificate and Social Security number: The Office of Personnel Management (OPM) tells me that they would consider those documents evidence of U.S. citizenship; the State Department tells me that's a mistake and that only a U.S. passport is proof of citizenship. OPM tells me they do not coordinate with the State Department when vetting applicants.)

A president wanting to clean up this mess would have to consider the scope of the Citizenship Clause. It does not appear there was ever a moment where a president said, "Yes, I think children born to tourists and illegal aliens are entitled to Social Security numbers and passports." The broad application of the Citizenship Clause is arguably on autopilot.

A president could direct his agencies to fall in line with his interpretation of the Supreme Court's rulings, which are arguably limited to children of permanently domiciled immigrants (the court has never squarely ruled on children born to tourists or illegal aliens). He could direct his agencies to issue Social Security numbers and passports only to newborns who have at least one parent who is a citizen or permanently domiciled immigrant.

Whether Trump worked with Congress to draft legislation or simply directed agencies to apply the Citizenship Clause more narrowly, the issue would likely end up at the Supreme Court. At that point, it might depend on what side of the bed Justice Anthony Kennedy woke up on that morning, or on whether Trump had appointed any new justices to the Supreme Court. Either way, there finally might be some clarity on the issue of birthright citizenship.

Feere is the legal policy analyst at the Center for Immigration Studies.